The acclaimed novel, originally written on a continuous roll of paper in a three-week period, has become a textbook for its followers, a magnum opus of nonsensical diction and ideals of American freedom on the open road. Kerouac’s tale of Beatnik friends in search of kicks claims to be semi-autobiographical, with the protagonist’s fascination, Dean Moriarty, based off Kerouac’s real life friend Neal Cassady.

The classic novel has seen several almost-made big-screen adaptations, with everyone from Marlon Brando to Brad Pitt wanting to tie their name to the classic, with no success until now. But these delayed attempts are understandable: how could anyone successfully turn Kerouac’s stream-of-consciousness novel into a film with a beginning, middle, and end?

But the challenge still exists, with The Motorcycle Diaries director Walter Salles taking a whack at it in 2012. So how did it measure? The following is a list of differences between Kerouac’s sensational novel and Salle’s star-studded rendition. Warning: Major spoilers ahead.

Marylou

From Kerouac’s initial description, Marylou—Dean Moriarty’s 16-year-old bride—is pigeonholed as your archetypal dumb blonde: ditzy, spontaneous, with a full head of bright blonde ringlets. Kristen Stewart was cast as Marylou at 17, before she played fair-skinned and often sullen Bella Swan in The Twilight series. Because these films preceded her On the Road role, they may have defined Stewart to the public as the anti-Mary Lou, who is neither ditzy nor carefree (and not fair-haired). Ironically, towhead Kirsten Dunst was cast as Camille, Dean’s second wife, who (while a minor point that certainly doesn’t spoil the role) is a brunette in the novel. And Stewart’s Marylou could have used some of Dunst’s usual perkiness.

The Road

Narrator Salvatore Paradise decides to leave his day-to-day life and join his friends, leaving the comfort of his mother’s New York home and setting his sights on Denver. Planning to hitchhike across the country, Sal gets off on the wrong foot. He hitches a ride with a man who takes him miles in the wrong direction, leaving him even farther away from his destination. In the film, this scene is left out, perhaps because it took up too much screen time or perhaps because it isn’t a major plot point. But this misstep sets the stage for the rest of young Sal Paradise’s journey. Sal is vulnerable, he doesn’t have the careless courage that his friend Dean has. He is naive about life on the road and as a delicate flower he is yet to be plucked.

Sex (With A Man)

In the novel, Dean is confronted with a situation in which he may or may not sleep with a man for money. In the book, the situation is vague, but it would seem that he doesn’t go through with the act. Yet in the film, Dean sleeps with the traveling salesman (played by Steve Buscemi) for cash, while Sal waits in the bathroom, uncomfortably peeking out to witness the transaction. Later, at a diner Dean apologetically says he only did it so they could have more money to travel on the road.

Sex (With Women)

Modern eyes see a different Dean Moriarty than the hero of Sal’s narration. And the film acknowledges this. Casting strong female actresses (Kristen Stewart, Kirsten Dunst, Amy Adams, Elisabeth Moss) to play otherwise sideline roles, Salles won’t let Dean off that easily. As a character who sleeps with (or attempts to sleep with) anyone who catches his eye, he arguably ruins the lives of many of the story’s females—leaving one woman for another, leaving one woman alone with a child and another on the way, and just leaving, period. Dean has a serious case of restless leg syndrome—that travels pointedly to his penis. But in Salle’s version, it’s not all kicks and giggles, as we are shown the hardship Dean’s first two wives face when he leaves to satisfy his sporadic and seemingly eternal immaturity.

The Tone

Devout fans of Kerouac’s classic might feel inclined to head out on their own open road adventure after reading the novel, but the same burst of youthful excitement might not be triggered after seeing the film. Salles’s portrayal of life on and off the road is more realistic. We see Sal working a number of poor-paying and mindless gigs, walking for long stretches on the frigid highway in winter, and often being left out of conversations with his “intellectual” friends. He is always tired, and usually ends up with the short end of the stick. Reminiscent of his heart-wrenching (albeit gorgeous) work on The Motorcycle Diaries, Salles is content with showing us a picture of life on the road for an unemployed kid in the ’40s as it may actually have been.

Dean’s Wives

As slutty as Dean Moriarty seemed to be, he was certainly a fan of holy matrimony. In the novel, he has three different wives, all in the span of a handful of years. In the film, he only has two—Marylou and Camille. Inez, a woman Sal introduces to Dean and Dean later marries and has a child with, doesn’t enter the film for more than a split second. In fact, I didn’t remember her presence at all, and had to confirm with IMDB that she did indeed make a small cameo in the film—but not as Dean’s wife. In the novel, Dean wants to marry many of the women he meets. For example, he fools around with a waitress named Beverly, and decides he “must” (a term he uses often with utmost enthusiasm and little persuasiveness) marry her once he can divorce Camille. In Salles’s version, two wives, instead of three, were enough for Dean.

Dean’s Abusiveness

In the book, Dean hurts his hand when he is hitting Marylou for sleeping with other men. In the film, Dean doesn’t show any signs of being abusive. But the scene in which we find out Dean hits his on-again-off-again flame, however short, is important in contributing to Dean’s development. He might be fun, careless, and seductive, but Sal’s hero can also be dangerous.

Dean’s Promiscuity

Dean’s constant promiscuity is heavily downplayed in the film. In the novel, if there is a woman in the same room as Dean, he’ll probably try to get her in bed. He treats women as his ultimate source of fun—and Sal lets us know that more than anything else, Dean just wants to have sex. Lots of sex. We get the idea in the film, but there are many scenes in the novel that make Dean seem less sexy, and more creepy. His sexual promiscuity is exposed in the film, but it does not evolve past youthful horniness and bad judgment. In the novel, Sal worships Dean for every aspect of his person, including his sometimes pedophilic (he becomes turned on by Old Bull Lee’s young daughter on a visit) and screw-anything-that-moves philosophy. To Sal, he is a modern philosopher.